Packagings of moulded pulp are used in a wide variety of fields and provide an environmental friendly packaging solution that is biodegradable. Products from moulded pulp are often used as protective packagings for consumer goods like for instance cellular phones, computer equipment, DVD players as well as other electronic consumer goods and other products that need a packaging protection. Furthermore moulded pulp objects can be used in the food industry as hamburger shells, cups for liquid content, dinner plates etc. Moreover moulded pulp objects can be used to make up structural cores of lightweight sandwich panels or other lightweight load bearing structures. The shape of these products is often complicated and in many cases they have a short expected time presence in the market. Furthermore the production series may be of relative small size, why a low production cost of the pulp mould is an advantage, as also fast and cost effective, way of manufacturing a mould.
In traditional pulp moulding lines, se for example U.S. Pat. No. 6,210,531, there is a fibre containing slurry which is supplied to a moulding die, e.g. by means of vacuum. The fibres are contained by a wire mesh applied on the moulding surface of the moulding die and some of the water is sucked away through the moulding die commonly by adding a vacuum source at the bottom of the mould. Thereafter the moulding die is gently pressed towards a complementary female part and at the end of the pressing the vacuum in the moulding die can be replaced by a gentle blow of air and at the same time a vacuum is applied at the complementary inversed shape, thereby enforcing a transfer of the moulded pulp object to the complementary female part. In the next step the moulded pulp object is transferred to a conveyor belt that transfers the moulded pulp object into an oven for drying.
Conventional pulp moulds which are used in the above described process are commonly constructed by using a main body covered by a wire mesh for the moulding surface. The wire mesh prevents fibres to be sucked out through the mould, but letting the water passing out. The main body is traditionally constructed by joining aluminium blocks containing several drilled holes for water passage and thereby achieving the preferred shape. The wire mesh is commonly added to the main body by means of welding. This is however complicated, time consuming and costly. Furthermore the grid from the wire mesh as well as the welding spots is often apparent in the surface structure of the resulting product giving an undesirable roughness in the final product. Furthermore the method of applying the wire mesh sets restrictions of the complexity of shapes for the moulding die making it impossible to form certain configurations in the shape.
WO2006057610 describes another kind of pulp moulding lines where the product is formed on a forming tool and subsequently pressed under heat and vacuum suction in a number of pressing steps. The product is thereafter dried in a microwave oven and ready for post treatment processes. A mould suitable for such pulp moulding lines was shown in WO2006057609. The moulding surface can be heated to 200° C. and above through a heat plate arranged to the bottom of the mould. The heat plate comprises a number of drilled holes which connects the mould to a vacuum box at the opposite side of the heat plate. However drilling holes in the heat plate may be costly and also lead to undesired waste of material. Another problem is that a lot of energy is needed to heat the moulding surfaces, via the heating plate.
Another kind of problem related to the tool design as presented in WO2006057609/10 is that the design of the pulp mould and also their production present some steps/features that imply high cost and/or undesired side effects.